Toilet tank



FIG. 1 is a perspective view of a toilet tank showing my new design;

FIG. 2 is a front elevational view thereof;

FIG. 3 is a top plan view thereof;

FIG. 4 is a rear view thereof;

FIG. 5 is a right side view thereof, the opposite side being a mirror image of the side shown; and

FIG. 6 is a bottom view thereof. 

CLAIM The ornamental design for a toilet tank, as shown and described. 